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Date: Thu, 29 Jan 2015 22:19:38 +0900
From: Namhyung Kim <namhyung@...nel.org>
To: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Ingo Molnar <mingo@...nel.org>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Jiri Olsa <jolsa@...hat.com>,
LKML <linux-kernel@...r.kernel.org>,
David Ahern <dsahern@...il.com>,
Adrian Hunter <adrian.hunter@...el.com>,
Andi Kleen <andi@...stfloor.org>,
Stephane Eranian <eranian@...gle.com>,
Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: [PATCH 29/42] perf tools: Protect dso cache fd with a mutex
On Thu, Jan 29, 2015 at 09:31:07AM -0300, Arnaldo Carvalho de Melo wrote:
> Em Thu, Jan 29, 2015 at 05:07:10PM +0900, Namhyung Kim escreveu:
> > When dso cache is accessed in multi-thread environment, it's possible
> > to close other dso->data.fd during operation due to open file limit.
> > Protect the file descriptors using a separate mutex.
> >
> > Signed-off-by: Namhyung Kim <namhyung@...nel.org>
> > ---
> > tools/perf/tests/dso-data.c | 5 ++
> > tools/perf/util/dso.c | 136 +++++++++++++++++++++++++++++---------------
> > 2 files changed, 94 insertions(+), 47 deletions(-)
> >
> > diff --git a/tools/perf/tests/dso-data.c b/tools/perf/tests/dso-data.c
> > index caaf37f079b1..0276e7d2d41b 100644
> > --- a/tools/perf/tests/dso-data.c
> > +++ b/tools/perf/tests/dso-data.c
> > @@ -111,6 +111,9 @@ int test__dso_data(void)
> > memset(&machine, 0, sizeof(machine));
> >
> > dso = dso__new((const char *)file);
> > + TEST_ASSERT_VAL("failed to get dso", dso);
> > +
> > + dso->binary_type = DSO_BINARY_TYPE__SYSTEM_PATH_DSO;
> >
> > /* Basic 10 bytes tests. */
> > for (i = 0; i < ARRAY_SIZE(offsets); i++) {
> > @@ -199,6 +202,8 @@ static int dsos__create(int cnt, int size)
> >
> > dsos[i] = dso__new(file);
> > TEST_ASSERT_VAL("failed to get dso", dsos[i]);
> > +
> > + dsos[i]->binary_type = DSO_BINARY_TYPE__SYSTEM_PATH_DSO;
>
> Those two are unrelated, please put them in a separate patch, one that I
> can even cherrypick ahead of the other patches.
It's a consequence of changing dso__data_read_offset() not to call
dso__data_fd() due to a performance reason. The binary_type was
determined during the dso__data_fd() before, but now it needs to be
set explicitly for this test.
In the original code, it was called everytime we access to the dso
cache just to check an error, I guess. But it's enough to check the
status field.
>
> > }
> >
> > return 0;
> > diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
> > index 11ece224ef50..ae92046ae2c8 100644
> > --- a/tools/perf/util/dso.c
> > +++ b/tools/perf/util/dso.c
> > @@ -213,6 +213,7 @@ bool dso__needs_decompress(struct dso *dso)
> > */
> > static LIST_HEAD(dso__data_open);
> > static long dso__data_open_cnt;
> > +static pthread_mutex_t dso__data_open_lock = PTHREAD_MUTEX_INITIALIZER;
> >
> > static void dso__list_add(struct dso *dso)
> > {
> > @@ -240,7 +241,7 @@ static int do_open(char *name)
> > if (fd >= 0)
> > return fd;
> >
> > - pr_debug("dso open failed, mmap: %s\n",
> > + pr_debug("dso open failed: %s\n",
> > strerror_r(errno, sbuf, sizeof(sbuf)));
> > if (!dso__data_open_cnt || errno != EMFILE)
>
> Ditto, another unrelated patch, please separate.
Ah, okay. I kept it since it's just a small change. But I'd like to
separate if it helps reviewing.
>
> > break;
> > @@ -382,7 +383,9 @@ static void check_data_close(void)
> > */
> > void dso__data_close(struct dso *dso)
> > {
> > + pthread_mutex_lock(&dso__data_open_lock);
> > close_dso(dso);
> > + pthread_mutex_unlock(&dso__data_open_lock);
> > }
> >
> > /**
> > @@ -405,6 +408,8 @@ int dso__data_fd(struct dso *dso, struct machine *machine)
> > if (dso->data.status == DSO_DATA_STATUS_ERROR)
> > return -1;
> >
> > + pthread_mutex_lock(&dso__data_open_lock);
> > +
> > if (dso->data.fd >= 0)
> > goto out;
> >
> > @@ -427,6 +432,7 @@ int dso__data_fd(struct dso *dso, struct machine *machine)
> > else
> > dso->data.status = DSO_DATA_STATUS_ERROR;
> >
> > + pthread_mutex_unlock(&dso__data_open_lock);
> > return dso->data.fd;
> > }
> >
> > @@ -531,52 +537,66 @@ dso_cache__memcpy(struct dso_cache *cache, u64 offset,
> > }
> >
> > static ssize_t
> > -dso_cache__read(struct dso *dso, u64 offset, u8 *data, ssize_t size)
> > +dso_cache__read(struct dso *dso, struct machine *machine,
> > + u64 offset, u8 *data, ssize_t size)
> > {
> > struct dso_cache *cache;
> > struct dso_cache *old;
> > - ssize_t ret;
> > -
> > - do {
> > - u64 cache_offset;
>
> While I understand that there was no need for this do { } while (0)
> construct in the first place, removing it in this patch is not
> interesting, as it is both unrelated to this patch and makes the it
> harder to review by just looking at the patch :-\ Please refrain from
> doing this in this patch.
Understood, sorry for bothering! :)
>
> A later patch that does _just_ that could be done, if you feel like
> doing it.
Okay.
>
> > + ssize_t ret = -EINVAL;
> > + u64 cache_offset;
> >
> > - ret = -ENOMEM;
> > + cache = zalloc(sizeof(*cache) + DSO__DATA_CACHE_SIZE);
> > + if (!cache)
> > + return -ENOMEM;
> >
> > - cache = zalloc(sizeof(*cache) + DSO__DATA_CACHE_SIZE);
> > - if (!cache)
> > - break;
> > + cache_offset = offset & DSO__DATA_CACHE_MASK;
> >
> > - cache_offset = offset & DSO__DATA_CACHE_MASK;
> > - ret = -EINVAL;
> > + pthread_mutex_lock(&dso__data_open_lock);
> >
> > - if (-1 == lseek(dso->data.fd, cache_offset, SEEK_SET))
> > - break;
> > + /*
> > + * dso->data.fd might be closed if other thread opened another
> > + * file (dso) due to open file limit (RLIMIT_NOFILE).
> > + */
> > + if (dso->data.fd < 0) {
> > + dso->data.fd = open_dso(dso, machine);
>
> Also please consider adding a backpointer to machine in the dso object,
> since you need to reopen it, so that we don't have to go on passing
> machine around to dso_cache__read(), etc.
Yeah, it's a pain to passing a machine pointer.
>
> This probably needs to be done in the patch that makes dso->data.fd to
> be closed due to limit.
I don't know which patch you are refering.. It already closes an fd
if it reaches the limit - what this patch does is protecting such
concurrent open and close when multi-thread is used.
Thanks,
Namhyung
>
> > + if (dso->data.fd < 0) {
> > + ret = -errno;
> > + dso->data.status = DSO_DATA_STATUS_ERROR;
> > + goto err_unlock;
> > + }
> > + }
> >
> > - ret = read(dso->data.fd, cache->data, DSO__DATA_CACHE_SIZE);
> > - if (ret <= 0)
> > - break;
> > + if (-1 == lseek(dso->data.fd, cache_offset, SEEK_SET))
> > + goto err_unlock;
> >
> > - cache->offset = cache_offset;
> > - cache->size = ret;
> > - old = dso_cache__insert(dso, cache);
> > - if (old) {
> > - /* we lose the race */
> > - free(cache);
> > - cache = old;
> > - }
> > + ret = read(dso->data.fd, cache->data, DSO__DATA_CACHE_SIZE);
> > + if (ret <= 0)
> > + goto err_unlock;
> >
> > - ret = dso_cache__memcpy(cache, offset, data, size);
> > + pthread_mutex_unlock(&dso__data_open_lock);
> >
> > - } while (0);
> > + cache->offset = cache_offset;
> > + cache->size = ret;
> > + old = dso_cache__insert(dso, cache);
> > + if (old) {
> > + /* we lose the race */
> > + free(cache);
> > + cache = old;
> > + }
> >
> > + ret = dso_cache__memcpy(cache, offset, data, size);
> > if (ret <= 0)
> > free(cache);
> >
> > return ret;
> > +
> > +err_unlock:
> > + pthread_mutex_unlock(&dso__data_open_lock);
> > + return ret;
> > }
> >
> > -static ssize_t dso_cache_read(struct dso *dso, u64 offset,
> > - u8 *data, ssize_t size)
> > +static ssize_t dso_cache_read(struct dso *dso, struct machine *machine,
> > + u64 offset, u8 *data, ssize_t size)
> > {
> > struct dso_cache *cache;
> >
> > @@ -584,7 +604,7 @@ static ssize_t dso_cache_read(struct dso *dso, u64 offset,
> > if (cache)
> > return dso_cache__memcpy(cache, offset, data, size);
> > else
> > - return dso_cache__read(dso, offset, data, size);
> > + return dso_cache__read(dso, machine, offset, data, size);
> > }
> >
> > /*
> > @@ -592,7 +612,8 @@ static ssize_t dso_cache_read(struct dso *dso, u64 offset,
> > * in the rb_tree. Any read to already cached data is served
> > * by cached data.
> > */
> > -static ssize_t cached_read(struct dso *dso, u64 offset, u8 *data, ssize_t size)
> > +static ssize_t cached_read(struct dso *dso, struct machine *machine,
> > + u64 offset, u8 *data, ssize_t size)
> > {
> > ssize_t r = 0;
> > u8 *p = data;
> > @@ -600,7 +621,7 @@ static ssize_t cached_read(struct dso *dso, u64 offset, u8 *data, ssize_t size)
> > do {
> > ssize_t ret;
> >
> > - ret = dso_cache_read(dso, offset, p, size);
> > + ret = dso_cache_read(dso, machine, offset, p, size);
> > if (ret < 0)
> > return ret;
> >
> > @@ -620,21 +641,42 @@ static ssize_t cached_read(struct dso *dso, u64 offset, u8 *data, ssize_t size)
> > return r;
> > }
> >
> > -static int data_file_size(struct dso *dso)
> > +static int data_file_size(struct dso *dso, struct machine *machine)
> > {
> > + int ret = 0;
> > struct stat st;
> > char sbuf[STRERR_BUFSIZE];
> >
> > - if (!dso->data.file_size) {
> > - if (fstat(dso->data.fd, &st)) {
> > - pr_err("dso mmap failed, fstat: %s\n",
> > - strerror_r(errno, sbuf, sizeof(sbuf)));
> > - return -1;
> > + if (dso->data.file_size)
> > + return 0;
> > +
> > + pthread_mutex_lock(&dso__data_open_lock);
> > +
> > + /*
> > + * dso->data.fd might be closed if other thread opened another
> > + * file (dso) due to open file limit (RLIMIT_NOFILE).
> > + */
> > + if (dso->data.fd < 0) {
> > + dso->data.fd = open_dso(dso, machine);
> > + if (dso->data.fd < 0) {
> > + ret = -errno;
> > + dso->data.status = DSO_DATA_STATUS_ERROR;
> > + goto out;
> > }
> > - dso->data.file_size = st.st_size;
> > }
> >
> > - return 0;
> > + if (fstat(dso->data.fd, &st) < 0) {
> > + ret = -errno;
> > + pr_err("dso cache fstat failed: %s\n",
> > + strerror_r(errno, sbuf, sizeof(sbuf)));
> > + dso->data.status = DSO_DATA_STATUS_ERROR;
> > + goto out;
> > + }
> > + dso->data.file_size = st.st_size;
> > +
> > +out:
> > + pthread_mutex_unlock(&dso__data_open_lock);
> > + return ret;
> > }
> >
> > /**
> > @@ -652,17 +694,17 @@ off_t dso__data_size(struct dso *dso, struct machine *machine)
> > if (fd < 0)
> > return fd;
> >
> > - if (data_file_size(dso))
> > + if (data_file_size(dso, machine))
> > return -1;
> >
> > /* For now just estimate dso data size is close to file size */
> > return dso->data.file_size;
> > }
> >
> > -static ssize_t data_read_offset(struct dso *dso, u64 offset,
> > - u8 *data, ssize_t size)
> > +static ssize_t data_read_offset(struct dso *dso, struct machine *machine,
> > + u64 offset, u8 *data, ssize_t size)
> > {
> > - if (data_file_size(dso))
> > + if (data_file_size(dso, machine))
> > return -1;
> >
> > /* Check the offset sanity. */
> > @@ -672,7 +714,7 @@ static ssize_t data_read_offset(struct dso *dso, u64 offset,
> > if (offset + size < offset)
> > return -1;
> >
> > - return cached_read(dso, offset, data, size);
> > + return cached_read(dso, machine, offset, data, size);
> > }
> >
> > /**
> > @@ -689,10 +731,10 @@ static ssize_t data_read_offset(struct dso *dso, u64 offset,
> > ssize_t dso__data_read_offset(struct dso *dso, struct machine *machine,
> > u64 offset, u8 *data, ssize_t size)
> > {
> > - if (dso__data_fd(dso, machine) < 0)
> > + if (dso->data.status == DSO_DATA_STATUS_ERROR)
> > return -1;
> >
> > - return data_read_offset(dso, offset, data, size);
> > + return data_read_offset(dso, machine, offset, data, size);
> > }
> >
> > /**
> > --
> > 2.2.2
--
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